The physical separation of the afterbirth from the neonate is critical to the survival of mammalian offspring. Mothers of most mammalian species, however, consume the afterbirth as part of the separation process. The behavior of consuming the afterbirth is referred to as placentophagia. Placentophagia does not seem to be directly critical to the survival of the offspring or of the mother, but little is known of the biological basis for the desire to eat placenta, or of the benefits derived from eating the placenta. My previous work with rats and mice has led to evidence that placentophagia at parturition and homeostatic feeding share a common neural basis in the absence of previous experience, that placentophagia is not initiated because of hunger, that nonpregnant females will engage in the behavior to a certain extent, and that there may be a two-gene basis for the difference observed in the response of genotypically different virgin mice toward placenta. My research proposal is designed to expand the preliminary research into a major investigation of the hormonal basis of placentophagia in rats, of the modification of the attitude of female rats towards placenta as a function of experience, and of the stimulus cues and mode of sensory reception involved in the modification of placentophagia as a function of experience.